Human A673 cells secrete high molecular weight EGF‐receptor binding growth factors that appear to be immunologically unrelated to EGF or TGF‐α

Abstract

Extracts of serum-free conditioned medium from human rhabdomyosarcoma A673 cells contain high molecular weight (HMW) transforming growth factors (TGFs) that can be partially purified by Bio-Gel P-100 and carboxymethyl (CM)-cellulose chromatography (Todaro et al: Proc Natl Acad Sci USA 77:5258, 1980). Reverse-phase high performance liquid chromatography (HPLC) revealed a principal peak of epidermal growth factor (EGF) radioreceptor assay (RRA) activity and anchorage-independent growth (AIG) activity that coeluted with 25-26% acetonitrile. If a trailing shoulder of EGF RRA activity from the CM-C chromatography was included in the material for HPLC analysis, additional active fractions were observed at 21-22% acetonitrile. Importantly, both active regions from HPLC failed to compete in radioimmunoassays under reduced and denatured conditions for human EGF (hEGF), human TGF-alpha (hTGF-alpha), or rat TGF-alpha (rTGF-alpha) and failed to give positive signals in Western blots under conditions in which TGF-alpha was readily detected when using an antisera raised against the 17 C-terminal amino acids of rTGF-alpha. Nonreducing sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) revealed EGF RRA and AIG activities in gel slices corresponding to Mr 15,000 and 22,000 in the 25-26% acetonitrile eluate and Mr 15,000, 20,000, 27,000, and 48,000 in the 21-22% acetonitrile eluate. The presence of multiple forms of EGF-receptor-binding peptides produced in vitro suggest size heterogeneity and possible immunologic diversity among high molecular weight members of the EGF/TGF-alpha family of growth-promoting polypeptides.

Expression of transforming growth factor alpha messenger rna in the normal and neoplastic gastro‐intestinal tract

“…Furthermore, when the amount of urinary protein used in the assay for TGF activity was increased, it appeared that low levels of the 35 kDa TGF activity may be present in the urine in all normal controls (Sherwin et al, 1983). In patients with brain tumours, urinary high-molecular-weight hTGF was indistinguishable from high-molecular-weight EGF in terms of EGF receptor binding activity, EGF immunoreactivity , and clonogenic activity (Stromberg et al, 1987). Studies in patients with hepatocellular carcinoma have detected TGFa immunoreactive materials in the urine of cancer patients, and also lower levels of TGFa immunoreactive material in the urine of normal controls (Yeh et al, 1987).…”

Production and response of a human prostatic cancer line to transforming growth factor-like molecules

“…Only one of three peaks demonstrated TGFx immunoreactivity and none were related to hEGF. It is interesting to note that many other types of cancer cells produce several molecular forms related to TGFa (Dickson et al, 1986;Stromberg et al, 1986;Salomon et al, 1987). The TGFa related molecular species produced by the DU145 prostate cell line may comprise the precursor form of TGFx or intermediate forms; further studies are required to distinguish between these possibilities.…”

Characterization of high molecular weight transforming growth factor .alpha. produced by rat hepatocellular carcinoma cells

“…There have been numerous other reports of bioactive higher molecular weight forms of TGFa (18-68K) found in supernatants of cultured human tumor cells (De Larco et al, 1985; Dickson et al, 1986;Stromberg, et al, 1986) and extracts of human platelets (Assoian et al, 1984) and urine (Kimball et al, 1984). In many cases, these proteins constitute the predominant TGFa activity, and their estimated size either equals or exceeds the molecular weight predicted for the transmembrane precursor.…”